The amount of success it takes for leaders to become overconfident isn't terribly large.

Optimistic people play a disproportionate role in shaping our lives. Their decisions make a difference; they are inventors, entrepreneurs, political and military leaders - not average people. They got to where they are by seeking challenges and taking risks.

A reliable way to make people believe in falsehoods is frequent repetition, because familiarity is not easily distinguished from truth. Authoritarian institutions and marketers have always known this fact.

In essence, the optimistic style involves taking credit for successes but little blame for failures.

Every night for the next week, set aside ten minutes before you go to sleep. Write down three things that went well today and why they went well...Writing about why the positive events in your life happened may seem awkward at first, but please stick with it for one week. It will get easier. The odds are that you will be less depressed, happier, and addicted to this exercise six months from now.

Survival prospects are poor for an animal that is not suspicious of novelty.

This is the essence of intuitive heuristics: when faced with a difficult question, we often answer an easier one instead, usually without noticing the substitution.